Method of transporting substances in a plasma stream to and depositing it on a target

ABSTRACT

A method of transporting substances in plasma streams to and depositing them on a target in which the vapors of two or more selected materials are turned into separate ionized plasmas in separate plasma generating chambers, the plasmas are effused from their respective chambers due to the difference in plasma density between the inside and outside of the chamber to form separate plasma streams and the plasma streams are joined to form a single stream which is conducted to the surface of a substrate by means of axial magnetic fields which also serve to converge the plasma streams. In another embodiment, a single stream is branched by a magnetic field to form plural streams which are conducted to different substrates or different points on the same substrate.

United States Patent [191 Tsuchimoto METHOD OF TRANSPORTING SUBSTANCESIN A PLASMA STREAM TO AND DEPOSITING IT ON A TARGET [75] Inventor:Takashi Tsuchimoto, Kodaira, Japan [73] Assignee: Hitachi, Ltd., Japan[22] Filed: May 19, 1972 [21] Appl. No.: 254,902

[30] Foreign Application Priority Data May 21, 1971 Japan 46-34629 May21, 1971 Japan 46-34630 May 21, 1971 Japan 46-34631 May 21, 1971 Japan46-34632 [52] U.S. Cl. 427/38; 148/175; 313/154;

[51] Int. Cl. C23C 11/08; BOSD 1/34; B05D l/38; BOSD 5/12 [58] Field ofSearch 117/933, 93.2, 207, 217, 117/93.1 GD, 106 A, 93; 250/492; 313/62,

[4 1 Oct. 28, 1975 3,297,465 l/l967 Connell ct al.... 1l7/93.1 GD

3,341,352 9/1967 Ehlers 1l7/93.3 3,344,357 9/1967 Blewett 313/623,419,487 12/1968 Robbins et a1... 1l7/93.1 GD

3,434,894 3/1969 Gale 250/492 3,445,722 5/1969 Scott et al.... 315/1113,496,029 2/1970 King et a1. 117/933 3,563,809 2/1971 Wilson 117/9333,571,642 3/1971 Westcott... 250/492 3,715,625 2/1973 Ehlers 315/1113,734,769 5/1973 Hirschfeld 117/933 Primary Examiner-John NewsomeAttorney, Agent, or FirmCraig & Antonelli [5 7] ABSTRACT A method oftransporting substances in plasma streams to and depositing them on atarget in which the vapors of two or more selected materials are turnedinto separate ionized plasmas in separate plasma generating chambers,the plasmas are effused from their respective chambers due to thedifference in plasma density between the inside and outside of thechamber to form separate plasma streams and the plasma streams arejoined to form a single stream which is conducted to the surface of asubstrate by means of axial magnetic fields which also serve to convergethe plasma streams. In another embodiment, a single stream is branchedby a magnetic field to form plural streams which are conducted todifferent substrates or different points on the same substrate.

54 Claims, 17 Drawing Figures [56] References Cited UNITED STATESPATENTS 2,953,750 9/1960 Christofilos 313/62 3,012,955 12/1961 Kulsrudet a1. 315/111 3,088,894 5/1963 Koenig 315/111 3,117,022 1/1964 Bronsonet a1 1l7/93.3 3,255,404 6/1966 Kidwell 315/111 U.S. Patent Oct.28, 1975Sheet 1 of8 3,916,034

FIG.

7 PRIOR ART FIG. 2

@ PR/OR ART COLLECTOR CURRENT I l 0 l Vs "PLASMA pamvrm V US. PatentOct.28, 1975 Sheet3of8 3,916,034

FIG. 5

FIG. 6

U.S. Patant Oct. 28, 1975 Sheet 4 of8 3,916,034

U.S. Patent Oct. 28, 1975 Sheet7 of8 3,916,034

US. Patent Oct.28, 1975 Sheet80f8 3,916,034

"A I AM /t\ WU I LI METHOD OF TRANSPORTING SUBSTANCES IN A PLASMA STREAMTO AND DEPOSITING IT ON A TARGET BACKGROUND OF THE INVENTION Field ofthe Invention 1. The present invention relates to a method and a devicefor transporting a desired material to a desired object by turning thematerial into plasma, and more particularly to the improvement of theinvention made by the present inventors, disclosed in the specificationof Japanese Pat. Publication No. 38801/70 (hereinafter referred to asthe Prior Art).

Description of the Prior Art The prior art invention is based in theprinciple that the stream of plasma composed of ionized gas can bedirected to the objective point due to the diffusing effect of theplasma itself and by the control of the plasma stream with axialmagnetic fields. The brief explanation of the prior art invention willbe described by reference to the attached drawings. In FIG. 1, referencenumeral 1 designates a plasma generating section or plasma generator forturning the vapor of a selected material into plasma through electricdischarge; 2 a plasma outlet opening of the plasma generator 1; 3 avoltage source for maintaining the plasma generator at a suitablepotential; 4 a plasma receiver or collector; 5 an ammeter for measuringelectric current carried by a plasma stream 8; 6 the wall of a containerto hermetically enclosing the plasma generator 1 and the plasmacollector 4, and 7 coils for generating axial magnetic field along thecontainer. The plasma generated in the generator I is effused out of theoutlet opening 2 due to the difference in density between the plasmainside the generator 1 and that outside the generator 1. The effusedplasma is converged by the magnetic field generated by the coils 7 toform a plasma beam 8, which is conducted to the plasma receiver 4 sothat the ionized material conveyed in the plasma beam is deposited onthe collector 4. The degree of converging the plasma stream and thedensity of plasma in the stream is changed depending upon the intensityof the axial magnetic field. If the axial field is too weak, the beam ofplasma is diverged so that the quality of plasma received by the unitarea of the plasma collector 4 is decreased. If the intensity of theaxial field is set higher than a certain level (for example, above 200gauss), the degree of convergence and the density can be kept constantwhile the plasma is traveling from the generator 1 to the collector 4.Thus, the axial field can be considered to serve as a magnetic pipe forthe plasma stream 8. FIG. 2 shows an empirical curve illustrating therelation between the potential V of the plasma applied through thegenerator l by means of the voltage source 3 and the plasma current Imeasured by the ammeter 5, i.e. current flowing from the plasma stream 8into the collector 4. If the plasma potential V is lower than the valueVe, the plasma current I is zero or negative since in this case theplasma stream 8 at the collector 4 the electrons excell in number thepositive ions, as seen in FIG. 2. If, on the other hand, the potential Vis larger than Ve, the positive ions excel in number the electrons sothat the current I turns positive. As the potential V is increased thecurrent I is increased, and when the potential V reaches the value V,the current I saturates at the value I, Under this condition, noelectron reaches the collector 4 due to repelling action and thecollector 4 gathers only positive ions.

Therefore, if the plasma current I takes the value I, under theapplication of the plasma potential higher than V it is considered thatthe atoms of the material corresponding in amount to the current I, bythe positive ions are being transported from the generator 1 to thecollector 4 in the plasma stream 8. Now, provided that the material tobe transported in plasma stream has a valence of 1 when it is turnedinto plasma in the generator 1, then the weight of the materialtransported in the plasma stream 8 per unit time: W (gram/sec.) isexpressed by the formula ls( ampere) M(gram) X e No where M is theatomic weight of the material, e the electric charge of an electron,i.e. 1.61 X 10* coulomb, and No Avogardros number 6.012 X 10 Now, if I,is 1 ampere, which is a practical value, and the area of cross sectionof the plasma stream is 1 cm, the weight W of the material received bythe collector 4 is about 0.29 mg/sec. for silicon and 0.27 mg/sec. foraluminum. In each case, the speed of deposition of the material Si or Alis very high, i.e. about lu/sec.

As described above, according to the prior art invention, a selectedmaterial can be deposited on a selected object at a great speed, and apredetermined amount of the material can be very accurately transportedto a predetermined area of the object. Thus, the accuracy and speed oftreatment to the prior art invention is much improved as compared withany conventional method of transporting substances in gas, liquid orsolid phase which is used to convey a desired material to a desiredplace as in vapor-deposition, sputtering, chemical synthesis,semiconductor doping, film formation and crystal growing. Moreover, themethod according to the prior art invention is quite different from thesubstance transporting method using implantation by accelerated ionbeam, which came to find its use in a variety of fields. The differencesare as follows.

First, the upper limit to the amount of material transported by anordinary accelerator is IOOuA in terms of ion beam, and even with anisotope separator such a limit is 10 to several 10s of milliamperes. Onthe other hand, according to the prior art method, it is possible todraw a current of mA to 1A.

Secondly, the conventional implantation method cannot transport theamount of material that is practically needed without immenselyincreasing the capacity of the overall apparatus to be used. It is,therefore, expensive and far from each operation so that its applicationto processes is limited. On the other hand, according to the prior artsystem, there is no need for a high voltage source for acceleration ofionized particles and therefore the apparatus to be used will be smallin size and easy of manipulation.

Thirdly, with the conventional implantation method, the energy of, forexample, Al ions is about 100 KeV and it is very difficult to obtain anion beam having a low energy of about 10 to several l0s of eV. In thefield of vapor-deposition or simiconductor technology a high energy ionbeam cannot be utilized but as ion beam having an energy of aboutseveral electron volts is most preferably used. For this reason, the ionbeam is decelerated when the conventional method is used forvapordeposition or semiconductor technology. In this case, however, theion beam is diverged in the decelerating process so that the quantity ofions reaching the target is much decreased. Accordingly, it will be hardto obtain a beam having sufficient ions per unit volume. On the otherhand, according to the prior art method, the energy necessary to conductthe plasma stream 8 up to the collector is a few volts to severalhundred volts in terms of the potential V of the plasma,

and in some cases the material can be transported to the collector 4only due to the diffusion effect, i.e. thermal energy, of the plasmaeven if the plasma potential V is reduced to zero.

As described above, the method of the prior art invention, i.e. JapanesePat. Publication No. 38801/70 by the present inventors, is quitedifferent in principle from any conventional method of transportingsubstance and takes a particular effect when applied for the treatmentof semiconductors and the like.

SUMMARY OF THE INVENTION One object of the present invention is toprovide an improved method of transporting substance in plasma.

Another'object of the present invention is to provide an improved methodwhich makes the best use of the merits of transporting substance inplasma stream, in which the kinds and the mixing proportions of thematerials transported to a substrate can freely be varied, and in whichthe shape, area and location of a film made of the transported materialcan be accurately determined.

An additional object of the present invention is to provide an improvedmethod in which material is turned into plasma and transported to asubstrate to form or to grow a single crystal of the material on thesubstrate.

A further object of the present invention is to provide an improvedmethod in which impurities or semiconductors are transported in plasmastream to semiconductor substrate to fabricate a semiconductor devicehaving p-n junctions or heterojunctions in or on the semiconductorsubstrate.

Yet another object of the present invention is to provide an improvedmethod of transporting substance in plasma stream.

Briefly state, the subject matter of the present invention will beconcentrated as follows. Namely, the vapor of a desired material isturned into plasma by means of a plasma generator, the plasma is effusedout of the plasma generator, and the plasma stream is guided by means ofaxial magnetic field to the surface of a substrate while being convergedby the same field. In particular, a plurality of plasma generators areprovided to produce plasma streams having different materials, thesestreams are deflected and mixed together with means for applyingmagnetic fields which are provided along the streams, and the mixedstream is guided to the substrate to form thereon a layer of compoundconstituted of the materials.

Accordingly, the device for embodying the method just describedcomprises a plurality of means for turning a material into plasma andfor ejecting the plasma in a fixed direction, means for deflecting theejected plasma streams, and means for combining the plasma streams, ifnecessary.

According to the present invention, different materials in plasma stateare blended together and the stream of the blended plasma is guided tothe substrate to deposit thereon a layer of compound consisting of thedifferent constituents. Moreover, if a crystal which can serve as a seedof single crystal is used as a substrate, the compound deposited on thesubstrate can be grown as single crystal.

According to the present invention, the simultaneous deposition ofdifferent materials on different areas of a substrate is possible.

According to the present invention, a swift transportation of substanceto the objective point is possible due to blending a plurality of plasmastreams having the same composition.

According to the present invention, a semiconductor is used assubstrate, impurities are turned into plasma, the plasma is guided to apredetermined portion of the substrate to deposit thereon theimpurities, and the substrate is heated upon or after the deposition ofthe impurities so as to diffuse the impurities into the semiconductorsubstrate and to fabricate a semiconductor device.

According to the present invention, a semiconductor in a plasma isdeposited on a substrate of a different kind of semiconductor tofabricate a semiconductor device having a heterojunction.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 schematically shows aconventional device for transporting substance in a plasma stream.

FIG. 2 shows an empirical curve representing the potential-currentcharacteristic of plasma.

FIG. 3 is a systematic block diagram of the constitution of a deviceused to embody the method according to thepresent invention.

FIG. 4 is a block diagram of a modified equivalent of the main part ofthe device shown in FIG. 3.

FIGS. 5 to 7 are cross sections of different plasma generatorsapplicable in the device according to the present invention.

FIG. 8 shows in cross section a plasma mixer and it bifurcated portionsas an embodiment of the present invention.

FIGS. 9 and 10 are perspective views of different scanners according tothe present invention.

FIG. 11 pictorially shows the method of diverging plasma stream, as anembodiment of the present invention.

FIG. 12 is a partially cross-sectional view of a device used to embodythe method according to the present invention.

FIG. 13 is a block diagram ofa device as another embodiment of thepresent invention.

FIG. 14 is an illustrative view of a further embodiment of the presentinvention.

FIG. 15 is a block diagram illustrative of an additional embodiment ofthe present invention.

FIg. 16 is an illustrative view of a still further embodiment of thepresent invention.

FIG. 17 is a block diagram illustrative of yet another embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EMBODIMENT 1 FIG. 3 showsschematically the constituents of a device for transporting substance ina plasma stream according to the present invention. In FIG. 3, as inFIG. 1, numerals l, 4, 7 and 8 designate plasma generating sections,plasma receiving sections, coils to generate axial magnetic flux forconverging plasma stream, and the courses of the plasma streams,respectively. However, in this case, a plurality of plasma generatingsections 1, i.e. source of plasma streams,'and/or plasma receivingsections 4, i.e. terminals of plasma streams, are provided. There arealso shown in FIG. 3 a plasma mixer section S for mixing the plasmastreams, a plasma branching section T for splitting a plasma stream intoseveral ones, a neutral particle remover section U, a plasma deflectingmeans V, indicators E for measuring the density of plasma, and plasmacomponent indicators F. In acutal embodiments, only one plasmagenerating section 1 may be provided to generate a single plasma stream8 to be conducted to the plasma branching section T while the plasmamixer section S is eliminated, or only one plasma receiving section 4may be provided to receive the single plasma stream leaving the plasmamixer section S while the plasma branching sectionT is eliminated.Moreover, according to the present invention, it is possible to proposea constitution, in which, as seen in FIG. 4, a plurality of plasmastream mixers S S S are provided for groups of plasma streams each ofwhich groups consists of some plasma streams and in which a plurality ofplasma streams branchers T T T each of which receives a single plasmastream and splits it into several streams are provided. Further, inorder to provide a more complicated network for plasma transportation,plasma stream mixers S S to join plasma streams and plasma streambranchers T T T to branch plasma streams may be inserted in the plasmachannels between the plasma stream mixers and branchers S S S ,...andT,T ,T ,T-,,....

The neutral particle remover U may be eliminated depending uponapplication.

Of the above described constituents of the device for transportingsubstance in plasma stream, the embodiments of plasma generating section1 will first be de-- scribed. FIG. 5 shows an embodiment of alow-voltage arc type plasma generator, in which a plasma sourcecontainer 9 serving also as an anode for are discharge is made of heatresistive electric conductor such as stainless steel or carbon. Asubstance 14 to be transported, contained in the vessel 9 is thermallyevaporated by means of a heating section 10 consisting of a heater 12insulated with non-conductive materials 11 and 13 and the vapor pressurewithin the container 9 is kept at about 10' Torr or less at whichdischarge can take place properly. A filament 16 serving as a cathodeelectrode for discharge is made of tungsten or tantalum wire having adiameter of, for example, 1 mm, and mounted on a pair of supporting rodsmade of conductive metal, piercing the wall of the container 9maintaining hermetical seal with the wall and insulated from the wall.The filament in operation is made to glow by the supply ofa current of100 A with a voltage of 3 V supplied across it. If under this conditiona d.c.

voltage of about 200 300 V is applied between the cathode filament l6and the wall of the container 9 as the anode, low-voltage arc dischargetakes place at a vapor pressure of about 1O- Torr to allow arc currentof I 3 A to flow. Since, in this case, the container 9 is placed in theaxial magnetic field, indicated by arrow B, produced by means of thecoil 7 and since the filament 16 as cathode is provided near a plasmaoutlet opening 17 cut in the wall of the container 9 which serves asanode, the established low-voltage are discharge is concentrated nearthe space between the filament l6 and the plasma outlet opening 17 toturn the vapor of material to be transported into high density plasma.The high density plasma is then effused out from the container 9 throughthe opening 17 into the outer atmosphere due to the difference indensity between inside and outside of the opening 17. And the axialfield is present in a predetermined direction due to the coil 7 so thatthe plasma stream 19 flowing out of the outlet opening 17 throughdiffusion effect is converged into a small-diameter beam and continuesto diffuse along the direction of the axial magnetic field. The axialmagnetic field can be considered to serve as a sort of pipe forconducting plasma stream therethrough because it enables plasma streamto flow through space while preventing the diameter of the stream fromincreasing. Hence, the course of plasma stream guided by the axial fieldmay hereafter be referred to as a magnetic pipe or magnetic channel.

Ifa material to be transported is a gas or a liquid having a high vaporpressure at room temperatures, it can be introduced into the container 9through a pipe 18 as shown in FIG. 5. The quantity of the fluid flow iscontrolled by an appropriate needle valve so that the vapor pressure ofthe material may stand appropriate to arc discharge. In case where amaterial to be transported has too high a melting point to obtain avapor pressure appropriate to are discharge due to an ordinary glowheating, it is necessary to introduce inert gas such as helium or argonas discharge carrier through the pipe 18. As a result, the obtainedplasma consists of a mixture of a large part of ions of the carrier gasand a small port of ions of the material to be transported.

FIG. 6 shows another embodiment of the invention, i.e. a plasmagenerating section of duoplasmatron type. In FIG. 6, numeral 20indicates an anode and numeral 21 designates a double cylinder having aninner cylinder whose free end serves as an intermediate electrode 21'and an outer cylinder which serves as a plasma container, andaccomodating a coil 27 to generate an axial magnetic field in the spacebetween the inner and outer cylinder. The anode 20 and the doublecylinder body 21 are both made of electrically conductive ferromagneticmaterial such as iron or the like. The magnetic flux induced by the coil27 is closed through a circuit comprising the anode 20, an insulatingpiece 22, the intermediate electrode 21 and the air gap between theelectrode 21' and the anode. A pair of lead wires 24 and a pipe 26 areinserted into the inner cylinder of the double cylinder body 21 isinsulated and hermetical condition by means of an insulating pad 25. Afilament 23 is mounted on the pair of lead wires 24, and is poweredthrough the wires 24. The pipe 26 serves to introduce the gas or vaporof material to be transported or carrier gas such as helium, argon orthe like, if necessary. Numeral 28 designates a plasma outlet openingcut in the anode 20. Now, the material in gaseous or vapor state to betransported is conducted through the pipe 26 into the inner cylinder andthe gas pressure in the inner cylinder is controlled so as to be kept atabout 10 Torr, the filament 23 is energized, and voltages of about 200 Vand about V are applied respectively between the filament 23 and theanode 20 and between the filament 23 and the intermediate electrode 21.

Then, a low-voltage arc discharge takes place so that a dischargecurrent of about 3A flows, the major portion of the current flowingbetween the filament 23 and the anode 20 and the minor portion betweenthe filament 23 and the electrode 21 The arc established due to thedischarge has its diameter limited by the inner diameter of the free endof the inner cylinder, i.e. intermediate electrode 21, and moreover isfocussed by the axial magnetic field having a high flux density as aresult of being concentrated in a narrow gap between the free end of theinner cylinder and the anode so that high density plasma is produced inthe discharge path between the intermediate electrode 21 and the anode20. The thus produced plasma effuses out from the outlet opening 28, asdescribed with FIG. 5. In this way, a high density plasma stream can beobtained, but the plasma generator of this type has a rather complicatedconstitution so that the utility factor of the vapor turned into plasmais largely lowered since part of the vapor of materials to betransported deposits on the wall of the container. Further, in casewhere chemically active gas such as oxygen or chlorine is introducedinto the container, the cathode filament 23 will be rapidly eroded sothat its operative life is shortened. In order to eliminate suchdrawbacks as mentioned above, inert gas such as helium or argon isintroduced into the container through the pipe 26 to cause low-voltagedischarge to take place, while a pipe 29 having a diameter larger thanthat of the outlet opening 28 is connected to the outer surface of theanode 20, as seen in FIG. 6, into which gas or vapor of the material tobe transported is conducted through a smaller pipe 30. The plasmagenerated near and inside the outlet 28 is jetted into the pipe 29 dueto the difference in density. Since there are in the jetted plasma avast number of ions of inert gas such as helium, for example, and ofelectrons given discharge energy, the gas or vapor introduced throughthe pipe 30 into the pipe 29 is ionized partially by the ions of theinert gas due to charge exchange therebetween and mostly by theelectrons in the plasma. Thus, a high density plasma 31 of the materialto be transported is produced in the pipe 29. The mechanism of the highdensity plasma being conveyed along the axial magentic field while beingfocussed by the field is the same as that described with FIG. 1 and FIG.5.

Fig. 7 shows a plasma generator of high frequency discharge type inwhich dischaage is established under the influence of high frequencyelectric field. For example, the gas or vapor of material to betransported is fed through a pipe 33 into a discharge tube 32 which ismade of insulating material such as glass or quartz and the gas pressureinside the tube 32 is maintained at about Torr. And ifa high frequencyvoltage of to 100 MHz is applied between a pair of ring electrodes 34provided on the tube 32 in appropriately spaced relation to each other,the gas of the material to be transported is turned into plasma due tothe electrodeless discharge taking place in the discharge tube 32, sothat plasma 36 streams out of the outlet opening 35. If it is desired tomaintain the potential of the plasma stream 36 at a predetermined level,it is only necessary to connect with an appropriate voltage source aprobe electrode 37 inserted in the tube 32. It should also be noted thatthe condenser coupling method of application of a high frequency voltagemay be replaced by an induction coupling method.

The conventional ion source used for, for example, the conventionalaccelerator or mass analyser has in principle the same constitution asthat used for the plasma generators described above and therefore it canbe used as a plasma source in the present invention if it is slightlymodified according to its purpose.

Reference should now be made to FIG. 8 in which is shown a plasma mixersection S, or S, to S as shown in FIGS. 3 and 4, which mixes a pluralityof plasma streams with one another. In this figure, reference numerals38a and 38b respectively designate evacuated pipes leaving plasmagenerators la and 1b; 39a and 39b flexed portions of the evacuated pipes38a and 38b, respectively; 40 a confluence pipe at which the pipes 38aand 38bjoin together; 41a and 41b coils for generating axial magneticfield respectively, in the pipes 38a and 38b; 42a and 42b deflectingcoils for generating axial magnetic field along the flexed portions 39aand 39b; and 43a and 43b coils for generating axial magnetic field inthe confluent pipe 40. The coils 43a and 43b are shown in FIG. 8 asseparately provided, however, they may be formed in a single unit.

The coils 41a, 42a and 43a generate continuous axial magnetic fieldalong the flexed channel from the pipe 38a to the confluence pipe 40 andthereby conduct the plasma stream 440 leaving the generator la to theconfluence pipe 40 while focussing the plasma stream 44a in the centerof the flexed channel. Similarly, the coils 41b, 42b and 43b generatecontinuous axial magnetic field along the flexed channel from the pipe38b to the confluence pipe 40 and thereby conduct the plasma stream 44bleaving the generator 1b to the confluence pipe 40 while focussing theplasma stream 44b in the center of the flexed channel. The plasmastreams 44a and 44b join together in the confluence pipe 40. In thisway, the diffemnt materials to be transported, included in the separateplasma streams are mixed together at the point S of confluence andthereafter the mixed plasma, i.e. mixed materials to be transported, isfurther conveyed. The just described constitution of the plasma mixersection is for the case where only two plasma generators are employed.And also in case where three plasma streams join together, as in FIG. 4,or where a plurality of plasma streams are mixed together, as in FIG. 3,the plasma mixer section to be used for this purpose is not differentfrom that used to two plasma streams except that the number of evacuatedpipes having flexed portions together with the number of associatedcoils for generating axial magnetic flux therein is increased. It shouldbe noted that when the mixer section shown in FIG. 8 is used as themixer section 8, or S shown in FIG. 4, the generators la and lb shown inFIG. 8 are to be substituted by the devices T and T or T and T Further,one of the plurality of plasma streams may be left non-deflected whilethe other plasma streams are deflected. Switches (not shown) may be usedin the exciting circuit of the coils so as to conduct any desired plasmastream to advan'ced stages or to block only a desired one of severalplasma streams so that it may not join the other.

The merits of deflecting a plurality of plasma streams to make them joinone another, which considerably add to the utility of the method oftransporting substance in the plasma streams, are counted as follows.

1. A great quantity of plasma can be transported by the use of aplurality of plasma generators each having a small capacity,- withoutemploying any plasma generator having a large capacitor which cannot beeasily fabricated or incorporated.

2. A plurality of materials which cannot coexist in a single plasmagenerator can be separately turned into the corresponding plasmas andthereafter be joined together.

3. Any desired material can be rapidly transported to its objectivepoints by switching over the axial magnetic field. And a variety ofmaterials can in turn be transported to one and the same objectivepoint. This is very important when a plurality of materials have to betransported which cannot be mixed during transportation in plasma streambecause of their chemical reactivity to one another.

4. The ratio of the material transported by the plasma stream 44a to theobject to the material transported by the plasma stream 44b to the sameobject can be arbitrarily controlled by controlling the ratio of therepetition period of excitation of the coils 41a to that of the coils41b.

Now, in order to give descriptions of plasma branching section T or T toT as shown in FIGS. 3 and 4, some modifications and alteration should bemade to FIG. 8. Namely, let the reference character S be substituted byT; let the direction of the arrow indicating the flow of plasma 44 beinverted; and let the plasma generators la and lb be substituted byplasma receiving sections 4 as shown in FIG. 3. And the function of theplasma branching section T is explained by reference to the thusmodified FIG. 8. (The plasma stream 44 now transported from the rightthrough the confluence pipe 40 by means of the combined effect of axialmagnetic fields generated by coils 43a and 43b is branched at thediverging point into two plasma streams 44a and 44b due to the branchingcomponents of the axial fields generated by deflecting coils 42a and42b). Moreover, it is clear that more than two plasma streams can bederived on the principle of branching and that the control of the plasmastreams 44a and 44b can be effected by controlling the exciting currentsfor the coils 41a, 42a and 41b, 42b since the plasma branching sectionhas a function inverse to that of the plasma mixer section. The meritsof branching a single plasma stream into several ones with such a plasmabranching section as described above, are as follows.

1. The simultaneous transportation of material from a single plasmasource to a plurality of tiny objects or objective points is possible.

2. The switching-over of material transportation to different objects orobjective points can be done by switching over the axial fields. Forexample, with a structure as shown in FIG. 9, the main plasma stream 46is branched out into a plurality of plasma streams 46a, 46b, 46c,directed to the different points on the object 45, and by sequentiallyswitching over the axial magnetic fields generated by means of coils47a, 47b, etc. for the plasma streams 46a 46b, etc. the object isreached by the plasma streams 46a, 46b, etc. sequentially in this orderso that the object 45 can be scanned by the plasma streams. Further, ifa flexed pipe 49 is connected with the pipe 48 for main plasma stream inrotatable and hermetical condition, as seen in FIG. 10, with a coil 50generating axial magnetic field wound about the flexed pipe 49, then thesurface of the object can be continuously scanned by the plasma streamwhen the rotatably connected flexed pipe 49 is rotated about the axis 51perpendicular to the surface of the object 45. In this case, thescanning follows a fixed locus. This way of canning is not one underconsideration, but the combination of the branching structure as shownin FIG. 9 and the rotating structure as shown in FIG. 10 may simplify toa certain extent the overall constitution.

According to these scanning methods, a rapid and exact transportation ofmaterial to a plurality of objective points and to a specific region onthe object having a predetermined pattern can be performed. In addition,these methods are meritorious also in that a single plasma stream havinga predetermined density can be diverged or converged to obtain a plasmastream having a larger or smaller diameter but the same density.

The practical artifice to diverge the plasma stream is shown in FIG. 11.Namely, the distance between the adjacent turns of the coil 55 ischanged at a point and the changed distance is maintained until anotherchange or restoration is needed. The coil 55 is wound thicker before thepoint and more spaced after the point so that the plasma stream 53 isdiverged at that point to be a thinner one 54, i.e. the density of thelatter being smaller than that of the former. This is not a technique ofbranching a plasma stream, which the present invention intends toprovide, but is a means to be effectively used in the method accordingto the present invention. This means can also be used to converge plasmastream if the direction of the stream is reversed. In this case, thedensity of the plasma stream after convergence is the same as that ofthe plasma stream before convergence since these plasma streams are bothdiffused ones.

3. By constituting the device as shown in FIG. 4 with the branching andcombined structures described above, a great number of plasma streamshaving different components and compositions can be obtained from ratherless plasma sources each having a single substance.

As described above, the utility of the prior art device for transportingsubstance in plasma stream as shown in FIG. 1 will be improved if themixing of plasma streams and/or the branching ofa plasma stream isperformed by providing magnetic deflecting means in the conducting pipesfor plasma streams and/or the branching of a plasma stream is performedby providing magnetic deflecting means in the conducting pipes forplasma streams of the device.

Now, the explanation will be made of an improved method of transportingsubstance in plasma streams, as one embodiment of the present invention,used to form thin films. Reference should be had to FIG. 12 for the helpof understanding. In the figure, reference characters la, 1b and 1mdesignate different plasma generating chambers; 56a, 56b and 56m pipesfor conducting the flows of the generated plasma therethrough; 57 aconfluence plasma pipe for joined plasma streams; 58a, 58b and 58m pipesfor branched plasma streams; 59a, 59b and 59m axial coils for the pipes56a 56b and 56m; 60 axial coils for the confluence pipe 57; 61a, 61b and61m axial coils for the pipes 58a, 58b and 58m; and 62a and 62b, 63a and63b, and 64a and 64B axial coils for defecting plasma streams, each ofthe coils 62a to 64a and 62b to 64b being partially shown. Numeral 65indicates a substrate on the surface of which thin film 66a,

66b and 66m is to be formed, and 67 a supporting platform on which thesubstrate 65 is rested. All the articles on the supporting platform 67are kept in vacuum by means of an enclosing wall of a container 6.

In case of forming blended film of Zn and Mg on the substrate 65 ofiron, Zn vapor and Mg vapor are turned into plasma in the plasmagenerating chamber la and lb, respectively. The thus obtained Zn plasmastream in the pipe 56a and Mg plasma stream in the pipe 56b jointogether by means of the deflecting coils 62a and 62b to form a blendedplasma stream consisting of Mg and Zn plasma in the confluence pipe 57.Then, the blended plasma stream is branched out into two plasma streamsto be conducted through the pipes'58a and 58b or three plasma streams tobe conducted through the pipes 58a, 58b and 58m by means of thedeflecting coils 63a, 63b and 63m. The branched blended plasma streamsare directed to the substrate 65 through deflection by means of thedeflecting coils 64a and 64b so that Zn and Mg ions transported in theblended plasma streams are deposited on the the surface of the substrate65 to form thin films 66a 66b or 66a, 66b and 66m. If, for example, itis desired to fonn only a thin film 66m, it is only necessary todeenergize the coils 61a and 61b for the branched pipe 58a 58b and thedeflecting coils 63a, 63b and 64a, 64b but to energize the coils 61malone. It is clear that in order to form thin films 66a 66b only thecoils associated with the branched pipe 58a 58b have to be energized.Also, in case where a plurality of thin films of a single substance, forexample, of Zn are formed on the substrate 65, only the plasma generatorlm is used to generate Zn plasma stream, and after the Zn plasma streamhas been led into the confluence pipe 57, it is branched out in the samemanner as described above.

Further, in order to have thin films 66a,- 66b and 66m respectively ofZn alone, Mg alone and the blend of Zn and Mg, only the 59a, 62a, 60,63a, 61a and 64a associated with the pipes 56a, 57, and 58a conductingthe Zn plasma stream from the plasma generator la to the film 66a areenergized to form the film 66a of Zn, then in like manner only the coilsassociated with the pipes conducting the Mg plasma stream from theplasma generator lb to the objective point 66b are energized to form thefilm 66b of Zn, and finally the coils 59a, 62a and 59b, 62b respectivelyfor the Zn plasma stream and the Mg plasma stream and the coils 60 and61m respectively for the confluence pipe 57 and the pipe 58m areenergized to form the blended film 66m of Zn and Mg. With this deviceshown in FIG. 12, however, it is impossible to simultaneously form thethin film 66a, 66b and 66m. If it is required to form the three film ata time, another structure has to be employed which is shown in FIG. 13as a block diagram resembling that shown in FIG. 4. Namely, Zn plasmastream from a plasma generator la is brached into two Zn plasma streamsby means of a plasma stream brancher Ta, while Mg plasma stream from aplasma generator 1b is branched into two Mg plasma streams by means of aplasma stream brancher Tb. One of the two Zn plasma streams is directedto the substrate to form thereon a Zn film 66a, and similarly one of thetwo Mg plasma streams is directed to the substrate to form thereon a Mgfilm 66b. The remaining one of the Zn plasma streams and the remainingone of the Mg plasma streams join together by means of a plasma streammixer S and the blended plasma of Zn and Mg is directed to the substrateto form thereon a blended film of Zn and Mg. Thus, the three thin filmscan be formed simultaneously.

The method according to the present invention is especially useful forthe formation of thin films in semiconductor devices. As one ofpreferred embodiments of the method, the formation of SiO film on Sisubstrate is explained. Plasmas of Si, 0 and Al are generated by theplasma generators 1a, lb and 1m. The Si plasma stream through the pipe560 and the 0 plasma stream through the pipe 56b join together in theconfluence pipe to form a blended plasma stream, which reaches thesurface of the Si substrate through at least one of the branched pipes58a, 58b and 58m to form thereon SiO film. Then, the generation andtransportation of the Si and O plasmas is ceased and, in turn, Al plasmais generated by the plasma generator lm. The Al plasma stream isconducted through the pipe 56m and the confluence pipe 60 up to thepoint of branching and it is' diverted to the pipe through which theblended plasma stream was guided. The Al plasma stream, passing throughthe selected pipe, reaches the previously formed SiO film and formedthereon an Al film. Thus, the formation of the SiO insulating film andthe Al conducting film for wiring can be easily and quickly perfomed onthe Si substrate by merely switching over the energization of axialcoils for plasma stream conducting pipes. Also, multi-layer circuit orwiring structure can easily be fabricated by repeating the abovedescribed processes. If boron B or phosphorus P is added to the SiOthrough simultaneous transportation of plasma, the so called doped oxidefilm can be resulted in.

in addition to the application to the semiconductor devices, the methodaccording to the present invention finds its use in the formation ofmetal multiple layer such as Au-Mo multiple layer constituted ofalternate Au and Mo layers. It will be needless to say that in this casethe coils for the Au and Mo plasma streams should be alternatelyenergized. Moreover, if a blended plasma stream consisting of two ormore kinds of metals is directed to the substrate 65 which is heated, asseen in FIG. 12, up to temperatures above 300C by means of anappropriate heating means 68, then a thin alloy film is formed in thesurface of the substrate 65.

Further, a thin film of chemical product such as oxide or halogenide canbe formed on the substrate by combining or switching over the magneticfields for the paths of plasmas of metal or other inorganic substancesand those for the paths of plasmas of halogenides or ox ides. Examplesof such compound films are, besides SiO film from Si and 0 A1 0 from Aland O and MoCl From Mo and C]. If the substrate 65 is heated above 300C,as described above, the chemical reac tion during the formation of suchcompound films will be promoted.

Still further, the superposed formation of different layers havingdifferent compositions such as A1 0 and si O or SiO and Si3N4 can beperformed according to the present invention.

According to the method of present invention, the diameter of the plasmabeam is as small as 3 to 4 mm due to the convergence effect of the axialmagnetic 7 field, the substrate it is sometimes preferable to increasethe diameter of the plasma beam by diverging the plasma beam accordingto the technique described with FIG. 1 l. A mask having perforations ina predetermined shape or a slit is placed in front of the targetsubstrate so that a thin film having the predetermined shape is formedon the substrate, as in the masking method used in the conventionalsemiconductor technology.

As has hitherto been described, the method according to the presentinvention is characterized in that a great number of different thinfilms can easily be produced and that the compositions of the differentthin films. can freely be varied. And this feature will be added to themerit of forming a thin film according to the method of transportingsubstance in plasma stream. Each of particles constituting plasma streamis an ion having a certain electric charge. Therefore, there appears theconcentration center of an infinite number of the ionized particles onthe surface of deposit of the substrate so that uniform and firm depositbecomes possible.

This advantageous feature is now combined with that according to thepresent invention.

Provided that, as described with FIG. 1, a power source 3 is connectedwith the plasma generator 1 to maintain the plasma stream at a potentialof, for example, V and that the receiver 4 or the substrate 65 in FIG.12 is grounded, each particle of the plasma stream is implanted in thesubstrate 65 at an energy of eVo (i.e. 100 eV when V0 is 100 V) toadhere very firmly to the same. If, on the other hand, Ar plasma istransported to an Si substrate at an energy of 300 eV, sputtering ontothe surface of the Si substrate takes place due to the energized argonatoms. So, if this sputtering is performed on the substrate before theformation of any desired film, the surface of thesubstrate on which athin film is formed is cleaned. And this will assure the firm adhesionof the resultant thin film to the substrate. In addition to the effectof cleaning the surface of the substrate, this sputtering method canalso be used to perforate the SiO layer. For this sputtering method,different from sputtering by ion beam, can effectively applied to suchan insulating material as SiO For example, by depositing a film ofconducting material such as Al on the SiO film after the perforatingoperation is formed a wiring layer.

EMBODIMENT 2 Another embodiment of the present invention will bedescribed which is applied to a case where the crystal of a material isgrown. For better understanding the embodiment reference should be hadto FIG. 9. In FIG. 14, the same reference numerals as in FIG. 12 havebeen applied to like constituents and the explanation of the partsmentioned with FIG. 12 is omitted here. Numeral 70 indicates a substratecrystal and crystals are grown at the portions 71a, 71b and 71m of thesubstrate crystal 70.

As a first example, crystal of GaAs is epitaxially grown on thesubstrate 70 made of a single crystal of GaAs. First, the vapors of Gaand As are turned into plasmas respectively in the plasma generator 1aand 1b and the thus obtained Ga and As plasma streams conductedrespectively through the pipes 56a and 56b are made to join together bymeans of the deflecting coils 62a and 62b to produce a blended plasmastream of Ga and As in the confluence pipe 57. The blended plasma streamis then branched into two or three streams conducted through the pipes580 and 58b or the pipes 58a, 58b and 58m by means of the deflectingcoils 63a and 63b, and therafter the branched plasma streams throughdeflection by the coils 64a and 64b and the plasma stream not deflectedare directed perpendicularly to the surface of the substrate so that Gaand As ions present mixed in the plasma streams coheres to the surfaceof the substrate 70 made of a single crystal of GaAs to grow crystals ofGaAs at the positions 71a, 71b and 71m. Now, if only the crystal 71m isdesired to be grown, it is only necessary to energize the axial coils61m alone, but not to energize the axial coils 61a and 61b for the pipes58a and 58b and the deflecting coils 63a, and 64a and 63b 64 b. It willtherefore be clear that if only the crystals 71a and 71b are desired tobe grown it is only necessary to energize the coils associated with thepipes 58a and 58b. As a second example, a single substance such as, forexample Si is grown at a plurality of portions of the surface of an Sisingle crystal 70. In this case, only the plasma generator 1m is used toproduce an Si plasma stream in the pipe 56m. The Si plasma stream, afterpassing though the confluence pipe 57, is branched out as describedabove. With the coils 61m energized, the Si plasma stream makes itsstraight way toward the substrate 70 to grow Si crystal thereon. As athird example, an Si intrinsic semiconductor crystal, a P-type siliconsemiconductor crystal and an N-type silicon semiconductor crystal aregrown respectively at the positions 71m, 71a and 71b on an intrinsicsemiconductor substrate 70 of silicon single crystal. In this case, Siplasma is generated in the chamber 1m and diffused into the pipe 56m toform a stream of Si plasma while the plasmas of a P-type impurity suchas I, and an N-type impurity such as Sb are generated respectively inthe plasma generating chambers la and lb and diffused into the pipes 56aand 56b to form streams of plasmas of I,, and Sb. First, the Si plasmastream is guided to the place 71m on the substrate 70 by means of theaxial coils 59m, 60 and 61m so as to form in the place 71m anepitaxially grown crystal of intrinsic silicon semiconductor. Then, onlythe I,, plasma stream is guided to the confluence pipe 57 by blockingthe Sb plasma stream by deenergizing the axial coils 59b for the pipe56b but advancing the 1,, plasma stream by energizing the axial coils59afor the pipe 56b. The 1,, plasma streams and the Si plasma streamjoin together in the confluence pipe 57. The blended plasma stream isfurther advanced through the pipe 57 by the energization of the axialcoils 60 until it reaches the branching point. If the coils 61m, 63b, 6lb and 64b are deenergized and if the coils 63a, 61a and 64a areenergized, the blended plasma of Si and I, reaches the place 6a on thesubstrate 65 to form theron an epitaxially grown P-type layer. In likemanner, if only the I, plasma stream is blocked by deenergizing theaxial coils for the pipe 56a, the Sb plasma stream is guided into theconfluence pipe 57 and therein blended with the Si plasma streams. Now,if only the coils 63b, 61b and 64b associated with the branched pipe 58bare energized, the blended plasma stream hits the portion 71b of thesubstrate 65 so that an N-type layer is epitaxially grown. Thus, thethree kinds of grown layers which were desired to be formed can beresulted in by the above described procedure. With this constitution asshown in FIG. 14, however, the simultaneous formation of these threelayers are impossible. In order to make possible such a simultaneoustransformation, a system should be employed which is shown in blockrepresentation in FIG. 15. Namely, the Si plasma stream from the plasmagenerator 1m is split by means of a plasma brancher T into threestreams, one of which is directed to the place 71m, another of whichjoins the 1,, plasma stream from the generator la in the mixer Ma sothat the blended plasma stream is directed to the place 71a, and therest of which joins the Sb plasma stream from the generator 1b in themixer Mb so that the blended plasma stream is directed to the place 71b.Therefore, the desired three kinds of layers can simultaneously formedas desired. Further, if branched channels leading to the place 71a, 71band 71m are provided for each of the blended plasma streams from themixers Ma and Mb and if those channels are appropriately switched overby suitably energizing and deenergizing the axial coils associated withthe channels, then the stream of the blended plasmas of Si and I, andthat of the blended plasmas of Si and Sb can be selectively directed toany one of the places 71a, 71b and 71m, e.g. place 71a, so that a P-N orN-P double-junction layer or a multi-junction layer having P-N-P-N-P- orN-P-N-P structure can be grown through epitaxial crystallization.Moreover, if the mixing proportion of the blended plasma consisting ofSi and 1,, to that consisting of Si and Sb is controlled, a multilayerconsisting of crystal grown layers having different doping quantity suchas P P, PP", n n or nn layers can be formed.

In sum, it is concluded that a variety of crystal grown layers can beobtained; the location, shape and area of the grown layers being freelyand accurately chosen, by the use of the suitable combination of theplasma stream mixing, branching and diverging methods described withFIGS. 3 and 4.

It is often necessary to heat the substrate crystal up to appropriatetemperatures with a heater 68 as shown in FIG. 14 while the crystal isgrown by plasma stream. Even in case where the substrate is heated,however, the temperatures at which Si crystal is grown are rather low,i.e. about 500C, so that no diffusion of impurity takes place in or nearthe junctions between superposed different layers as of such amultilayer as described above. Accordingly, abrupt step junctions can beobtained. This is one of considerable merits in fabricatingsemiconductor device.

According to the method embodying the present invention, the formationof a heterojunction in semiconductor devices becomes possible. Oneexample of forming a heterojunction will be described by reference toFIG. 14. Germanium Ge is used as the substrate 70, and Ga and As areturned into plasma in the plasma generator la and lb, respectively.These plasmas of Ga and As are conveyed to a predetermined place on thegermanium substrate to grow thereon a GaAs crystal.

According to the method of the present invention, the diameter of theplasma beam is as small as 3 to 4 mm due to the convergence effect ofthe axial magnetic field, and in order to form a thin film on a largerarea of the substrate it is sometimes preferable to increase thediameter of the plasma beam by diverging the plasma beam according tothe technique described with FIG. 11. A mask having a perforations in apredetermined shape or a slit is placed in front of or on the targetsubstrate so that an epitaxial crystal having the predetermined shape isgrown on the substrate, as in the masking method used in theconventional semiconductor technology.

As has been described, the method according to the present invention ischaracterized in that a great numher of different crystals can easily begrown and that the compositions of the different grown crystals canfreely be varied. And this feature will be added to the merits ofgrowing a crystal according to the method of transporting substance inplasma stream. Further, provided that, as described with FIG. 1, a powersource 3 is connected with the plasma generator 1 to maintain the plasmastream at a potential of, for example, V0 and that the receiver 4 or thesubstrate in FIG. 14 is grounded, each particle of the plasma stream atthe surface of the substrate 70 has an energy of eVo (i.e. 50 eV when V0is 50 V) so that even if the temperature of the substrate 70 is low thecrystal can be grown due to the part of energy absorbed in thesubstrate.

If the Si plasma is transported to the substrate of Si crystal at anenergy smaller than the association energy of silicon atoms, i.e. 10 eV,the whole energy 10 eV is distributed as thermal energy to the particlesof the Si plasma arrived at the substrate without causing sputtering anddefects on the substrate itself so that the crystal can be grown withoutflaw and defect even in case where the temperature of the substrate israther low. This is true for the process of growing the crystal ofcompound semiconductor.

If, on the other hand, Ar plasma is transported to Si substrate at anenergy of 300 eV, sputtering onto the surface of the substrate of Sicrystal takes place due to the energized argon atoms. So, if thissputtering is performed on the substrate prior to the groving of adesired crystal, the surface of the substrate is cleaned and becomesfree of contaminations so that the crystal can be grown in a preferablecondition.

EXAMPLE 3 This is a process of doping a semiconductor substrate withimpurities according to the method of present invention in whichsubstance is transported in plasma stream. For the better understandingof the embodiment reference should be had to FIG. 16. In FIG. 16 thesame reference numerals as in FIG. 12 has been applied to likeconstituents and the explanation thereof is not repeated here, thoughnewly introduced parts are not the case. A substrate is shown as havingthree portions 81a, 81b and 81m doped with impurities.

For example, in case of simultaneously doping a substrate 80 of siliconsingle crystal with As and B having different diffusion coefficients,the vapors of arsenic As and boron B are first turned into plasmarespectively in the plasma generator la and lb so that the As and Bplasma streams produced in the pipe 56a and 56b are forward conveyed bymeans of the coils 59a and 59b and join each other, by means of thecoils 62a and 62b, in the confluence pipe 57 to produce a stream ofblended plasma consisting of As and B therein. Then, the blended plasmastream is branched into three streams by means of the deflecting coils63a and 63b or two streams by means of the same deflecting coils and thecoil 61m. The plasma stream in the pipe 58m is directed by means of thecoil 61m perpendicularly to the surface of the portion 81m of thesubstrate 80 while the plasma streams in the pipes 58a and 58 b aredirected perpendicularly to the surfaces of the portions 81a and 81b ofthe substrate 65 by means of the deflecting coils 64a and 64b,respectively. Therefore, the ions of As and B conveyed in the blendedplasma streams stick to and become deposited on the surfaces of theportion 81a, 81b or 81m. Now, if the substrate is heated up totemperatures of lOOl200C by means of a suitable heating device such asshown indicated at 68 in FIG. 16, the As and B atoms will be diffusedinto the Si substrate 65 according to their diffusion coefficients.Since the diffusion coefficient of B is greater than that of As, twon-pn junction layers in superposition can be optained if the Sisubstrate is of n-type, If, on the other hand, the blended plasma streamis contacted with the substrate 80 while the latter is heated at 1000 toI200C, both the impurities As and B are diffused into the substrate 80as soon as they have come in contact therewith so that doping along withdiffusion process becomes possible. Moreover, if the supporting platform67 is shifted horizontally, it is also possible to sucessively dope withimpurities a plurality of substrates 80 placed on the platform 67. Ifonly the portion 81m is desired to be doped with impurities, it is onlynecessary to energize the coils 61m alone with the coils 61a and 61b forthe branched pipe 58a and 58b and the deflecting coils 63a, 63b and 64a,64b deenergized. It is, therefore, clear that if only the portion 81a or81b is desired to be doped only the coils associated with pipe 58a 58bneeds to be energized with the coil 61m deenergized. If only asubstance, for example, As is desired to be deposited on a plurality ofportions of the substrate80, only the plasma 1m is used to produce Asplasma stream in the pipe 56m. The As plasma stream is guided into theconfluence pipe 57 and thereafter branched out as described above.

Now, if the portions 81a, 81b and 81m of the substrate 80 need to bedoped respectively with As, B and both of As and B, the followingprocedure should be carried on. Namely, the plasma generator la is firstoperated to produce As plasma stream in the pipe 560 and at the sametime only the coils 59 a, 62a, 60, 63a, 61a and 64a associated with thepipes 56a, 57 and 58a are energized so that only the portion 81a isdoped with As atoms. Then, the plasma generator 1b is operated toproduceB plasma stream in the pipe 56b and at the same time only thecoils 59b, 62b, 60, 63b, 61b and 64b associated with the pipes 56b, 57and 58b are energized so that only the portion 81b is doped with Batoms. And finally, both the plasma generators la and 1b are operated toproduce As and B plasma streams respectively in the pipe 56a and 56b andsimultaneously only the coils 56a and 56b, 62a and 62b, 60 and 61m areenergized so that the blended plasma is transported to the portion 81m,resulting in doping the portion 81m with both As and B atoms. With thedevice having such a constitution as shwon in FIG. 16, however, it isimpossible to simultaneously dope the portions 81a, 81b and 81m withimpurities. In order to make possible such a simultaneous doping, asystem should be employed which is shown in block representation in FIG.17. Namely, the As plasma stream from the generator la is split by meansof a plasma brancher Ta into two streams while the B plasma stream fromthe generator 1b is split by means of a similar brancher- Tb into twostreams. One of the two As plasma streams is directly guided to theportion 81a while one of the two B plasma streams is also directlyconducted to the portion 81b. The other of the two As plasma streams andthe other of the two B plasma streams join together in the plasma mixerS and a blended plasma consisting of As and B is produced, which isdirected to the portion 81m. With this constitution, therefore, it ispossible to perform the simultaneous doping.

With the conventional device of similar type in which there is used onlyone plasma generator, it is very difficult to dope a substrate with aplurality of impurities, even with two kinds of impurities such as Asand B, in such a manner that the proportion of the doped impurities maybe kept constant if the careful adjustment of the proportion in quantityof As plasma to B plasma in the generator is neglected. According to thepresent invention, on the other hand, a plurality of impurities to besimultaneously doped in the same area are separately turned into thecorresponding plasmas, the density of each plasma is individuallycontrolled, and thereafter each plasma stream joins another in theconfluence pipe to produce a blended plasma in a prede termined blendproportion. Thus, no difficult blending of different plasmas in thefixed proportions is needed.

In addition, the use of the branching means, diverging means andscanning means as described above will make possible the control of thedensities of the individual plasmas and therefore the control ofblending proportion of the plasmas.

Even in case where a plurality of impurities are used, the variouscombination of the impurities and the control of the blending proportionwill be possible by the combined use of the above described means, asdescribed with FIGS. 3 and 4. In addition, by further branching oneconducting pipe into some branched ones, as seen in FIG. 9, doping ofdifferent portions of the same substrate or of several substrates willbe possible, and the control of the quantity of material doped into eachportion and of doping pattern will also be facilitated.

It should here be noted that the doping of various metals withimpurities can also be preformed according to the method of the presentinvention.

According to the method of this embodiment, the diameter of the plasmabeam is as small as 3 to 4 mm due to the convergence effect of the axialmagnetic field. This is especially useful fo the fabrication ofmicrosemiconductor devices. However, in order to dope with impurities alarger area of the substrate it is sometimes preferable to increase thediameter of the plasma beam by diverting the plasma beam according tothe technique described above. A mask having perforations in apredetermined shape or a slit is placed in front of the substrate so asto make possible doping in the predetermined pattern or doping in a tinyarea, as in the masking method used in the conventional semiconductortechnology.

As has been described, the method according to the present invention ischaracterized in that a great number of different doping processes canbe chosen and that the proportions of the doped impurities can freely bevaried. And this feature will be added to the merits of the method oftransporting substance in plasma stream.

Further, if, as described with FIG. 1, a power source 3 is connectedwith the plasma generator 1 to maintain the plasma stream at a potentialof, for example, V0 and if the receiver or the substrate in FIG. 16 isgrounded, then each particle of the plasma stream reaching the surfaceof the substrate 80 is implanted in the substrate 80 at an energy of eVo(i.e. 400 eV when V0 is 400 V). Therefore, in case of doping a Sisubstrate with B atoms, the B atoms are implanted in the substrate tothe depth of 14 A. The depth of implantation is determined by the kindof ions in the plasma and the energy of the ionized particles. If the Batoms as impurity are implanted in the depth of about A at an energy of400 eV as above, the implanted impurities occupy all the lattice pointsof the Si substrate which is free of lattice defects as a result ofannealing and therefore completely activated so that a very thinjunction is formed on the Si substrate. Namely, the same result asobtained by the implantation of B atoms into Si substrate according tothe ion beam method, can be attained.

If, as described above, impurities having energy are doped into thesubstrate kept at high temperatures, the impurities are implanted in thesubstrate to a small depth so that a great number of lattice vacanciesare created in the surface of the substrate. These lattice vacancies areswiftly diffused into the inner region of the substrate due to the heatapplied to the substrate so that the distribution of the concentrationof lattice vacancies larger than that corresponding to the temperatureof the substrate is established. This means that a domain having adiffusion coefficient greater than that corresponding to the temperatureof the substrate is formed deep in the substrate. Thus, the dopedimpurities are subjected to enhanced diffusion. With Si substrate,enhanced diffusion takes place at temperatures in excess of 600C andthis effect multiplies as the temperature rises. Also in this case,diffusion of impurities takes place in Si substrate even if thetemperature of the substrate is not so high as l000 to 1200C at whichimpurities are diffused into the Si substrate, so that the describedmethod is applicable to the diffusion treatment required in the processof fabricating general semiconductor devices or the isolation treatmentrequired in the process of fabricating integrated circuits, just as hotimplantation in the ion implantation method is applicable to suchprocesses.

The method according to the present invention can enjoy another effectthat is also obtained by hot implantation in the ion implantationmethod. Namely, Si substrate is previously doped with impuritiesaccording to the method of the present invention or the conventionalthermal diffusion technique and the substrate is heated. Inert neutralatoms of, for example, neon or helium are transported at an energy of400 eV to the substrate according to the method of the present inventionto generate lattice vacancies in the surface of the doped and heatedsubstrate so that the impurities concentrated in a doped layer aresubjected to accelerated diffusion due to the generated latticevacancies.

When argon plasma is transported to the Si substrate at an energy of 300eV, the energized argon atoms cause sputtering on the surface of thesubstrate. So, if this sputtering is performed on the substrate prior tothe desired doping, the surface of the substrate is cleaned so thatdoping may be done in a preferable condition.

The method of the present invention can also perform the same thermaldiffusion as carried out by the Doped Oxide method in which an oxidefilm containing impurities at high concentration, deposited on thesubstrate, is used as a source of impurities for diffusion. Namely,besides the impurities, Si and 0 are turned into plasmas and the blendedplasma containing the impurities, Si and O is transported to thesubstrate surface. Then, a SiO film containing sufficient impurities isformed on the surface of the substrate so that the impurities in the SiOfilm can be used as a source of impurities for diffusion.

I claim:

1. A method of transporting material to and depositing it on a target,comprising the steps of:

turning a first material and a second material different from said firstmaterial into respective plasmas in respective first and second plasmagenerator chambers, each having a small opening,

effusing said plasmas from said first and second chambers,

forming said plasmas into first and second plasma beams by means ofaxial magnetic fields, deflecting at least one of said first and secondplasma beams to join one to the other,

conducting the thus joined plasma beam to a desired portion of thesurface of said target to make the material in said joined plasma beamdeposit on said target.

2. A method according to claim 1, wherein the diameter of said joinedplasma beam is increased at the immediate front of said surface of saidtarget.

3. A method according to claim 2, wherein a mask having at least oneopening is provided near the surface of said target and the materialtransported in said joined plasma beam is selectively deposited only onthe surface of said target corresponding to said opening.

4. A method according to claim 1 wherein said target is subjected toheat treatment at deposition of said material in said joined plasma beamon said target.

5. A method according to claim 1, wherein a voltage is applied betweensaid material in said plasma and said target in such a manner that saidplasma is kept positive in potential with respect to said target.

6. A method according to claim 1, wherein said first material is zinc,said second material is magnesium and said target is an iron plate, anda thin film of zinc and magnesium is formed on said iron plate.

7. A method according to claim 1, wherein said first material issilicon, said second material is oxygen and said target is asemiconductor plate, and a compound layer of silicon and oxygen isformed on the surface of said semiconductor plate.

8. A method according to claim 1, wherein said first material issilicon, said second material is nitrogen and said target is asemiconductor plate, and a compound layer of silicon and nitrogen isformed on the surface of said semiconductor plate. I

9. A method according to claim 7, which includes subsequent steps of:

turning a metal into plasma in a third plasma generator chamber,

effusing the plasma from said third chamber,

forming the plasma from said third chamber into a' third plasma beam bymeans of an axial magnetic field, and

deflecting said third plasma beam toward said compound layer of siliconand oxygen formed on said semiconductor plate;

whereby a thin layer of said metal is formed on said compound layer.

10. A method according to claim 9, wherein after said metal thin layeris formed, a compound beam of silicon and oxygen is again directed tosaid metal thin layer to form a further compound layer of silicon andoxygen thereon.

11. A method according to claim 1, wherein said target is asemiconductor plate, said first material is a metal and said secondmaterial is oxygen, whereby a thin layer of metal oxide is formed onsaid semiconductor plate.

12. A method of transporting material to and depositing it on a targetcomprising the steps of:

turning silicon, oxygen and phosphorus into respective plasmas inrespective plasma generating chambers,

effusing said respective plasmas from said respective chambers,

forming the effused plasmas into plasma beams respectively by means ofaxial magnetic fields, deflecting at least two of said three plasmabeams to join said three beams into a single beam, and conducting thejoined plasma beam to the target which is a semiconductor plate;

whereby a compound layer of silicon, oxygen and phosphorus is formed onsaid semiconductor plate.

13. A method of transporting material to and depositing it on a targetcomprising the steps of:

turning silicon, oxygen and boron into respective plasmas in respectiveplasma generating chambers, effusing said respective plasmas from saidrespective chambers,

forming the effused plasmas into plasma beams respectively by means ofaxial magnetic fields, deflecting at least two of said three plasmabeams to join said three beams into a single beam, and conducting thejoined plasma beam to the target which is a semiconductor plate;

whereby a compound layer of silicon, oxygen and boron is formed on saidsemiconductor plate.

14. A method of transporting material to and depositing it on a targetof a semiconductor plate, comprising the steps of:

turning silicon, oxygen and an inert gas into respective plasmas inrespective plasma generating chambers,

effusing said respective plasmas from said respective chambers,

forming the effused plasmas into plasma beams respectively by means ofaxial magnetic fields, directing the plasma beam of said inert gas to aspot on the surface of said semiconductor plate to thereby clean thesurface at the spot, and subsequently directing plasmas of silicon andoxygen, after joining both plasma beams into a single beam, to saidcleaned spot; whereby a compound layer of silicon and oxygen is formedon the cleaned surface of said semiconductor plate.

15. A method of transporting material to and depositing it on a targetof a semiconductor plate, comprising the steps of:

turning silicon, oxygen and an inert gas into respective plasmas inrespective plasma generating chambers,

effusing said respective plasmas from said respective chambers,

forming the effused plasmas into plasma beams respectively by means ofaxial magnetic fields, joining the plasma beams of silicon and oxygeninto a single beam,

directing the joined beam to the semiconductor plate to form a compoundlayer of silicon and oxygen on said semiconductor plate, and

subsequently directing the plasma beam of said inert gas to a part ofthe deposited compound layer to thereby remove said part of the compoundlayer by sputtering.

16. A method according to claim 15, which includes subsequent steps of:

turning a metal into a plasma in a further plasma generating chamber,

effusing the plasma of said metal from the chamber,

forming the effused plasma into a plasma beam by means of an axialmagnetic field, and

directing the plasma beam of said metal to an opening made in saidcompound layer by said sputtering with the plasma beam of the inert gasto thereby deposit said metal in said opening.

17. A method of transporting material to and depositing it on asubstrate comprising the steps of:

generating at least two plasma beams of at least one substance; joiningtogether said generated plasma beams to form a joined plasma beam;guiding said joined plasma beam to at least a part of one Surface ofsaid substrate; and

forming a layer of said at least one substance on said part of onesurface of said substrate.

18. A method according to claim 17, wherein each of said plasma beams isformed of an identical substance.

19. A method according to claim 17, wherein each of said plasma beams isformed of a different substance.

20. A method according to claim 19, wherein said layer is a compound ofsaid different substances.

21. A method according to claim 20, wherein said substrate is a singlecrystal.

22. A method according to claim 21, wherein said layer of said compoundis a single crystal layer of said compound.

23. A method according to claim 21, wherein said singie crystalsubstrate is a semiconductor material.

24. A method according to claim 23, wherein said at least two plasmabeams consist of a first and second plasma beams, each of said first andsecond plasma beams being formed of a respective first and secondmaterial.

25. A method according to claim 24, wherein said first material is thesame semiconductor material as said single crystal substrate and saidsecond material is a conductivity determining material for saidsemiconductor material.

26. A method according to claim 17, wherein said plasma beams are guidedby means of magnetic pipes.

27. A method according to claim 26, wherein said magnetic pipes includeat least one bend such that neutral particles existing in said plasmabeams are removed.

28. A method according to claim 17, wherein said joined plasma beam isat a positive potential with respect to said surface.

29. A method according to claim 28, wherein said positive potential is400 eV or less.

30. A method according to claim 17, wherein said 65 step of guidingfurther includes branching said joined plasma beam into a plurality ofplasma beams.

31. A method according to claim 30, wherein said at least a part of onesurface includes a plurality of differ-

1. A METHOD OF TRANSPORTING MATERIAL TO AND DEPOSITING IT ON A TARGET,COMPRISING THE STEPS OF: TURNING A FIRST MATERIAL AND A SECOND MATERIALDIFFERENT FROM SAID FIRST MATERIAL INTORESPECTIVE PLASMAS IN RESPECTIVEFIRST AND SECOND PLASMA GENERATOR CHAMBERS, EACH HAVING A SMALL OPENING,EFFUSING SAD PLASMAS FROM SAID FIRST AND SECOND CHAMBERS, FORMINGPLASMAS INTO FIRST AND SECOND PLASMAS BEAMS BY MEANS OF AXIAL MAGNETICFIELDS, DEFLECTING AT LEAST AONE OF SAID FIRST AND SECOND PLASMA BEAMSTO JOIN ONE TO THE OTHER, CONDUCTING THE THUS JOINED PLASMA BEAM TO ADESIRED PORTION OF THE SUFACE OF SAID TARGET TO MAKE THE MATERIAL INSAID JOINED PLASMA BEAM DEPOSIT ON SAID TARGET.
 2. A method according toclaim 1, wherein the diameter of said joined plasma beam is increased atthe immediate front of said surface of said target.
 3. A methodaccording to claim 2, wherein a mask having at least one opening isprovided near the surface of said target and the material transported insaid joined plasma beam is selectively deposited only on the surface ofsaid target corresponding to said opening.
 4. A method according toclaim 1, wherein said target is subjected to heat treatment atdeposition of said material in said joined plasma beam on said target.5. A method according to claim 1, wherein a voltage is applied betweensaid material in said plasma and said target in such a manner that saidplasma is kept positive in potential with respect to said target.
 6. Amethod according to claim 1, wherein said first material is zinc, saidsecond material is magnesium and said target is an iron plate, and athin film of zinc and magnesium is formed on said iron plate.
 7. Amethod according to claim 1, wherein said first material is silicon,said second material is oxygen and said target is a semiconductor plate,and a compound layer of silicon and oxygen is formed on the surface ofsaid semiconductor plate.
 8. A method according to claim 1, wherein saidfirst material is silicon, said second material is nitrogen and saidtarget is a semiconductor plate, and a compound layer of silicon andnitrogen is formed on the surface of said semiconductor plate.
 9. Amethod according to claim 7, which includes subsequent steps of: turninga metal into plasma in a third plasma generator chamber, effusing theplasma from said third chamber, forming the plasma from said thirdchamber into a third plasma beam by means of an axial magnetic field,and deflecting said third plasma beam toward said compound layer ofsilicon and oxygen formed on said semiconductor plate; whereby a thinlayer of said metal is formed on said compound layer.
 10. A methodaccording to claim 9, wherein after said metal thin layer is formed, acompound beam of silicon and oxygen is again directed to said metal thinlayer to form a further compound layer of silicon and oxygen thereon.11. A method according to claim 1, wherein said target is asemiconductor plate, said first material is a metal and said secondmaterial is oxygen, whereby a thin layer of metal oxide is formed onsaid semiconductor plate.
 12. A method of transporting material to anddepositing it on a target comprising the steps of: turning silicon,oxygen and phosphorus into respective plasmas in respective plasmagenerating chambers, effusing said respective plasmas from saidrespective chambers, forming the effused plasmas into plasma beamsrespectively by means of axial magnetic fields, deflecting at least twoof said three plasma beams to join said three beams into a single beam,and conducting the joined plasma beam to the target which is asemiconductor plate; whereby a compound layer of silicon, oxygen andphosphorus is formed on said semiconductor plate.
 13. A method oftransporting material to and depositing it on a target comprising thesteps of: turning silicon, oxygen and boron into respective plasmas inrespective plasma generating chambers, effusing said respective plasmasfrom said respective chambers, forming the effused plasmas into plasmabeams respectively by means of axial magnetic fields, deflectinG atleast two of said three plasma beams to join said three beams into asingle beam, and conducting the joined plasma beam to the target whichis a semiconductor plate; whereby a compound layer of silicon, oxygenand boron is formed on said semiconductor plate.
 14. A method oftransporting material to and depositing it on a target of asemiconductor plate, comprising the steps of: turning silicon, oxygenand an inert gas into respective plasmas in respective plasma generatingchambers, effusing said respective plasmas from said respectivechambers, forming the effused plasmas into plasma beams respectively bymeans of axial magnetic fields, directing the plasma beam of said inertgas to a spot on the surface of said semiconductor plate to therebyclean the surface at the spot, and subsequently directing plasmas ofsilicon and oxygen, after joining both plasma beams into a single beam,to said cleaned spot; whereby a compound layer of silicon and oxygen isformed on the cleaned surface of said semiconductor plate.
 15. A methodof transporting material to and depositing it on a target of asemiconductor plate, comprising the steps of: turning silicon, oxygenand an inert gas into respective plasmas in respective plasma generatingchambers, effusing said respective plasmas from said respectivechambers, forming the effused plasmas into plasma beams respectively bymeans of axial magnetic fields, joining the plasma beams of silicon andoxygen into a single beam, directing the joined beam to thesemiconductor plate to form a compound layer of silicon and oxygen onsaid semiconductor plate, and subsequently directing the plasma beam ofsaid inert gas to a part of the deposited compound layer to therebyremove said part of the compound layer by sputtering.
 16. A methodaccording to claim 15, which includes subsequent steps of: turning ametal into a plasma in a further plasma generating chamber, effusing theplasma of said metal from the chamber, forming the effused plasma into aplasma beam by means of an axial magnetic field, and directing theplasma beam of said metal to an opening made in said compound layer bysaid sputtering with the plasma beam of the inert gas to thereby depositsaid metal in said opening.
 17. A method of transporting material to anddepositing it on a substrate comprising the steps of: generating atleast two plasma beams of at least one substance; joining together saidgenerated plasma beams to form a joined plasma beam; guiding said joinedplasma beam to at least a part of one surface of said substrate; andforming a layer of said at least one substance on said part of onesurface of said substrate.
 18. A method according to claim 17, whereineach of said plasma beams is formed of an identical substance.
 19. Amethod according to claim 17, wherein each of said plasma beams isformed of a different substance.
 20. A method according to claim 19,wherein said layer is a compound of said different substances.
 21. Amethod according to claim 20, wherein said substrate is a singlecrystal.
 22. A method according to claim 21, wherein said layer of saidcompound is a single crystal layer of said compound.
 23. A methodaccording to claim 21, wherein said single crystal substrate is asemiconductor material.
 24. A method according to claim 23, wherein saidat least two plasma beams consist of a first and second plasma beams,each of said first and second plasma beams being formed of a respectivefirst and second material.
 25. A method according to claim 24, whereinsaid first material is the same semiconductor material as said singlecrystal substrate and said second material is a conductivity determiningmaterial for said semiconductor material.
 26. A method according toclaim 17, wherein said plasma beams are guided by means of magneticpipes.
 27. A method according to claim 26, wherein saiD magnetic pipesinclude at least one bend such that neutral particles existing in saidplasma beams are removed.
 28. A method according to claim 17, whereinsaid joined plasma beam is at a positive potential with respect to saidsurface.
 29. A method according to claim 28, wherein said positivepotential is 400 eV or less.
 30. A method according to claim 17, whereinsaid step of guiding further includes branching said joined plasma beaminto a plurality of plasma beams.
 31. A method according to claim 30,wherein said at least a part of one surface includes a plurality ofdifferent surface portions, each of said plurality of plasma beams beingguided to a respective one of said plurality of different surfaceportions.
 32. A method according to claim 30, wherein each of saidplurality of plasma beams is further guided to a respective differentlocation at said one surface.
 33. A method according to claim 17,wherein said surface is heated during the step of forming said layer.34. A method according to claim 33, wherein said surface is heated to atemperature of about 500*C.
 35. A method according to claim 33, whereinsaid surface is heated to a temperature of between about 1000* to1200*C.
 36. A method of transporting material to and depositing it on asubstrate comprising the steps of: generating at least one plasma beamof at least one substance; guiding said at least one plasma beam to atleast one substrate including branching said at least one plasma beaminto a plurality of plasma beams; and forming a layer of said at leastone substance at each of a plurality of locations.
 37. A methodaccording to claim 36, wherein said at least one substrate includes aplurality of different substrates, each of said plurality of plasmabeams being further guided to a respective one of said plurality ofdifferent substrates.
 38. A method according to claim 36, wherein eachof said plurality of plasma beams is guided to a respective differentlocation at said at least one substrate.
 39. A method of transportingmaterial to and depositing it on a substrate comprising the steps of:generating a first material into a first plasma in a first plasmagenerating chamber having a small opening; generating a second materialinto a second plasma in a second plasma generating chamber having asmall opening; effusing each of said generated plasmas through each ofsaid small openings by force of a difference in plasma density; formingeach of said effused plasmas into respective plasma beams by means ofmagnetic pipes provided by axial magnetic fields; transporting saidrespective plasma beams through said magnetic pipes; joining togethersaid transported plasma beams to form a joined plasma beam; directingsaid joined plasma beam to at least one part of one surface of saidsubstrate; and forming a layer of said first and second materials onsaid at least one part of one surface of said substrate.
 40. A methodaccording to claim 39, further comprising the step of widening saidjoined plasma beam.
 41. A method according to claim 40, wherein saidstep of widening said joined plasma beam includes adjusting thecorresponding axial magnetic field.
 42. A method according to claim 39,further comprising the step of branching said joined plasma beam duringsaid step of directing by adjusting the corresponding axial magneticfield, thereby causing widening of the cross-section of said joinedplasma beam to allow divergence of separate branches of said plasma beamto be formed by components of the corresponding axial magnetic fields.43. A method according to claim 39, further comprising the step ofbranching at least one of said plasma beams prior to said step oftransporting.
 44. A method of transporting material to and depositing iton a substrate comprising the steps of: turning a first and a secondmaterial into respective plasmas respectively in a first and a sEcondchamber, each of said chambers having a small opening; effusing each ofsaid respective plasmas through each of said small openings; formingeach of said respective plasmas into respective plasma beams by means ofaxial magnetic fields; joining together said respective plasma beams toform a joined plasma beam; directing said joined plasma beam to thesurface of a single crystal substrate; and forming a single crystal of acompound consisting of said first and second materials on said singlecrystal substrate.
 45. A method according to claim 44, wherein saidsingle crystal substrate is GaAs, said first material is gallium andsaid second material is arsenic.
 46. A method according to claim 44,wherein said single crystal substrate is a semiconductor, said firstmaterial being the same semiconductor material as said substrate, andsaid second material being one for determining the conductivity of saidsemiconductor when added thereto.
 47. A method according to claim 44,wherein said substrate is subjected to heat treatment at a temperaturehigher than 500* when a single crystal of said materials is grown onsaid substrate.
 48. A method according to claim 44, wherein apredetermined voltage is applied between each of said plasmas and saidsubstrate in such a manner that each of said plasmas is kept morepositive than said substrate in potential.
 49. A method according toclaim 44, wherein a mask having at least one opening of a desiredpattern is disposed between said joined plasma beam and said substrate.50. A method according to claim 49, wherein said mask is a SiO2 layerformed directly on the surface of said substrate.
 51. A method oftransporting material to and depositing it on a substrate comprising thesteps of: turning silicon, oxygen and an impurity material intorespective plasmas respectively in first, second and third plasmagenerating chambers, each of said chambers having a small opening;effusing each of said respective plasmas through each of said smallopenings; forming each of said respectively effused plasmas intorespective plasma beams by means of axial magnetic fields; joiningtogether said plasma beams to form a joined plasma beam; directing saidjoined plasma beam to the surface of the substrate; and forming acompound layer of silicon and oxygen containing said impurity materialon said surface of the substrate.
 52. A method according to claim 51,wherein said substrate is subjected to heat treatment.
 53. A methodaccording to claim 51, wherein said compound layer is a single crystalof silicon and oxygen containing said impurity material.
 54. A methodaccording to claim 51, wherein said compound layer is formed to apredetermined thickness.